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We show that if an exponential polynomial $$\sum _{i=1}^m P_i(z)e^{Q_i(z)}$$ , where $$P_i$$ , $$Q_i\in \mathbb C[z]$$ , is a dth power, $$d\ge 2$$ , of an entire function g, then g itself is also an exponential polynomial. We also study when a multivariable polynomial with moving targets of slow growth evaluated at unit arguments can be a dth power of an entire function. Finally, we formulate a boundary case of the Green–Griffiths–Lang conjecture for projective spaces with moving targets.

In the melanin synthesis process, oxidative reactions play an essential role, and it is a good strategy to inhibit melanin production by reducing oxidative stress. Fullerene and its derivatives, or the complexes, were considered as strong free-radical scavengers, and we further applied multilayered sp2 nanocarbons to discover melanin synthesis inhibitory mechanisms. In the present study, we used novel nanomaterials, such as multiwalled carbon nanotubes (MWCNTs), short-type MWCNTs, graphene oxide nanoribbons (GONRs), and short-type GONRs, as anti-oxidative agents to regulate melanin production. The results showed that GONRs had better anti-oxidative capabilities in intracellular and extracellular oxidative stress analysis platforms than others. We proposed that GONRs have oxygen-containing functional groups. In the 2',7'-dichlorodihydrofluorescein diacetate assay, we found out GONR could chelate metal ions to scavenge reactive oxygen species. In the molecular insight view, we observed that these nanomaterials downregulated the melanin synthesis by decreasing microphthalmia-associated transcription factor-related gene expressions, and there were similar consequences in protein expressions. To sum up, GONRs is a potential agent as a novel antioxidant and skin-whitening cosmetology material.

A novel core–shell structured multiwall carbon nanotube–graphene oxide nanoribbon (MWCNT@GONR) and a nitrogen-doped MWCNT@GONR (N-MWCNT@GONR) were synthesized through a microwave energy-assisted unzipping process and utilized as anodes for Escherichia coli-based microbial fuel cells (MFCs) for the first time. To evaluate the electrochemical performance of the MFCs, we measured the electrochemical activity and charge transfer in MFCs with MWCNT, N-MWCNT@GONR, and MWCNT@GONR anodes. Compared to the MFC with the MWCNT anode (970 mW m−2), the MFCs with the N-MWCNT@GONR and MWCNT@GONR anodes exhibit higher power densities of up to 3444 and 3291 mW m−2, respectively. Both the oxygen and nitrogen functional groups on the MWCNT@GONR and N-MWCNT@GONR contribute to good biocompatibility, which greatly enhances the charge transfer efficiency and biofilm formation on the anode surface. Our results suggest that MWCNT@GONR and N-MWCNT@GONR are outstanding and promising anode materials for MFCs.

For every semi-abelian variety over a function field K of characteristic zero, we show that any subgroup of its S-integral K-valued points is discrete in the product of its local points over an infinite set of places of K, where S is a finite set of places of K.

In this study, a non-enzyme glucose fuel cell is assembled and shows high energy density in neutral solution at moderate temperature. The anodic material, graphene sheets grafted with platinum and palladium (PtPd/G), is prepared by polyol method to oxidize glucose. The cathode material, nitrogen-doped graphene oxide nanoribbons (NGONR) is prepared by a microwave process, and shows great oxygen reduction capability in neutral cerebrospinal fluid (CSF) solution. After cell assembly, test results show that the performance of the glucose fuel cell is significantly affected by oxygen concentration, glucose concentration and operating temperature. Compared with the enzyme glucose fuel cell, the non-enzyme glucose fuel cell can generate power not only at room or human body temperatures, but within a temperature range from 5 to 80 °C. The cell power density increases with increasing operating temperature. The assembled fuel cell can produce a maximum power density of 24.9 µW/cm2 in a neutral 10 mM CSF and 8 mM glucose solution at 80 °C with an oxygen purge flow.

For every affine variety over a global function field, we show that the set of its points with coordinates in an arbitrary rank-one multiplicative subgroup of this function field satisfies the required property of weak approximation for finite sets of places of this function field avoiding arbitrarily given finitely many places.

We propose a function-field analog of Pisot's d-th root conjecture on linear recurrences, and prove it under some “non-triviality” assumption. Besides a recent result of Pasten-Wang on Buchi's d-th power problem, our main tool, which is also developed in this paper, is a function-field analog of a GCD estimate in a recent work of Levin and Levin-Wang. As an easy corollary of such a GCD estimate, we also obtain an asymptotic result.

We give a natural sufficient condition which ensures the finiteness of the number of integral points on a projective space omitting finitely many hyperplanes defined over a one-dimensional function field of positive characteristic. In this setting, when the number of hyperplanes is 2 n + 2 , where n is the dimension of the ambient projective space, we use this natural condition to explain and sharpen an earlier result of the second named author, which provides a concrete condition on the coefficients of the linear forms producing hyperplanes such that the above finiteness property is satisfied.

In this work, through a heteroatom-doping process and the subsequent base washing strategy, a new type of metal-free nitrogen- and sulfur-codoped graphene nanoribbons (BW-NS-rGONRs) were synthesized. It was found that a considerable amount of carbonaceous oxidative debris resided in graphene oxide nanoribbons (GONRs) produced from unzipping multiwalled carbon nanotubes has a great effect on the electrocatalytic activity of rGONRs. After removing the adsorbed oxidative debris by base washing, the obtained BW-NS-rGONRs exhibited high electrical conductivity and rich defect active sites, endowing the BW-NS-rGONRs enhanced electrocatalytic activity for TNT reduction. The electrochemical sensing platform established from the BW-NS-rGONRs showed a highly sensitive and selective response to TNT with a wide linear range from 0.0008 to 5.1 ppm and a detection limit of 0.1 ppb. Moreover, the BW-NS-rGONRs-based TNT detection platform demonstrated good cyclic stability and reproducibility. Most importantly, the BW-NS-rGONRs-based sensing platform can be successfully used for TNT determination in tap water and lake water samples. The superb sensing performance is attributed to the abundant active sites from dual doping of N and S atoms, the enhanced electrical conductivity and full exposure of the active sites of BW-NS-rGONRs after base washing treatment.

Die Untersuchung von Biomarkern und injizierten theranostischen Nanomaterialien in Geweben und Organen spielt eine zentrale Rolle bei zahlreichen medizinischen Verfahren von der Krebsdiagnose bis hin zur Arzneimittelverabreichung. Zu diesem Zweck kann die elektrochemische Rastersondenmikroskopie hochaufgeloste Abbildungen der raumlichen Verteilung von wichtigen Biomolekulen ohne optische Interferenzen liefern. Wir haben weiche Mikroelektroden zum Abtasten grosflachiger und dicker Gewebeschnitte und Organe, die in eine Elektrolytlosung eingetaucht sind, verwendet. Die Messung amperometrischer Strome wurde durch den lokalen Fluss redoxaktiver Spezies ermoglicht, welche lokal und spezifisch durch Biomarker und Nanomaterialien in den Proben erzeugt wurden. Die biologischen Verteilungen von Graphenoxidnanostreifen in Mauseleber, von prognostischen Proteinbiomarkern in menschlichem Hautkrebsgewebe und von redoxaktiven Proteinen in Mauseherzen wurden separat abgebildet.

In this work, we demonstrate multi-bandgap photodetectors with an inherently lattice-matched structure by the natural stacking of graphene oxide nanoribbons. The stacked multilayer graphene oxide nanoribbons are produced by unzipping multi-walled carbon nanotubes. A correlation study between image inspection and photoelectrical characterization of stacked graphene oxide nanoribbon devices is performed in specific chips. Transmission electron microscopy images reveal the presence of a multilayer graphene oxide nanoribbon with gradually increasing widths, suggesting that multilayer graphene oxide nanoribbons with decreasing bandgaps could innately act as low-pass photon energy filters and serve to increase the spectral absorption window in these photodetectors. Photoelectrical measurements show visible-light spectrum absorption, which suggests that the various energy bandgaps of the multi-layer graphene oxide nanoribbons contribute toward the increased bandwidth in photon absorption. Furthermore, photo-responsivities on the order of 10 A/W with a stable photo-switching behavior as well as fast response times are observed. The response times range from 2 ms in the membrane devices down to a few hundred of μs in the suspended devices due to elimination of the substrate effect. Based upon this correlation study, we believe that this stacked multilayer graphene oxide nanoribbon structure with gradually varying widths is a promising candidate towards the development of novel high performance photodetectors and optoelectronics.

In this work, PtPd concave nanocubes anchored on graphene nanoribbons (PtPd-rGONRs) were successfully fabricated through a hydrothermal process. The structural characterizations confirmed that PtPd concave cubes with an average size of around 11 nm have been successfully synthesized and they are uniformly assembled on the surface of rGONRs. The electrochemical measurements demonstrated that the PtPd-rGONRs composite-modified glassy carbon electrode (GCE) shows much enhanced current signals for TNT reduction, which is 4 and 12-fold higher than rGONRs and bare glassy carbon electrode, respectively. The PtPd-rGONRs exhibited a wide linear range for TNT detection from 0.01 to 3 ppm with the sensing limit of 0.8 ppb. Moreover, the PtPd-rGONRs showed excellent detection stability for the determination of TNT. Most importantly, the PtPd-rGONRs-based electrochemical detection platform can be successfully applied to TNT detection in tap water and real lake water samples. The present study indicates that graphene nanoribbon-supported nanocrystals are promising in designing high performance electrochemical sensors for explosives detection.

Chemical vapor deposition (CVD) graphene is reported to effectively prevent the penetration of outer factors and insulate the underneath metals, hence achieving an anticorrosion purpose. However, there is little knowledge about their characteristics and corresponding corrosion properties, especially for those prepared under different parameters at low temperatures. Using electron cyclotron resonance chemical vapor deposition (ECR-CVD), we can successfully prepare graphene nanostructures on copper (Cu) at temperatures lower than 600 &deg, C. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and potentiodynamic polarization measurements were used to characterize these samples. In simulated seawater, i.e., 3.5 wt.% sodium chloride (NaCl) solution, the corrosion current density of one graphene-coated Cu fabricated at 400 &deg, C can be 1.16 &times, 10&minus, 5 A/cm2, which is one order of magnitude lower than that of pure Cu. Moreover, the existence of tall graphene nanowalls was found not to be beneficial to the protection as a consequence of their layered orientation. These correlations among the morphology, structure, and corrosion properties of graphene nanostructures were investigated in this study. Therefore, the enhanced corrosion resistance in selected cases suggests that the low-temperature CVD graphene under appropriate conditions would be able to protect metal substrates against corrosion.

In this study, the growth of graphene by chemical vapor deposition (CVD) on SUS304 stainless steel and on a catalyzing Ni/SUS304 double-layered structure was investigated. The results indicated that a thin and multilayered graphene film can be continuously grown across the metal grain boundaries of the Ni/SUS304 stainless steel and significantly enhance its corrosion resistance. A 3.5 wt% saline polarization test demonstrated that the corrosion currents in graphene-covered SUS304 were improved fivefold relative to the corrosion currents in non-graphene-covered SUS304. In addition to enhancing the corrosion resistance of stainless steel, a graphene coating also ameliorates another shortcoming of stainless steel in a corrosive environment: the formation of a passive oxidation layer on the stainless steel surface that decreases conductivity. After a corrosion test, the graphene-covered stainless steel continued to exhibit not only an excellent low interfacial contact resistance (ICR) of 36 mΩ cm2 but also outstanding drainage characteristics. The above results suggest that an extremely thin, lightweight protective coating of graphene on stainless steel can act as the next-generation bipolar plates of fuel cells.

We demonstrate the microwave-assisted synthesis of short graphene oxide nanoribbons (GONRs) through unzipping cut multiwalled carbon nanotubes (MWCNTs). Transmission electron microscopy and dynamic light scattering spectroscopy were used to examine the length, size, and morphology, i. e. unzipping level, of our various products. The nanotube core and nanoribbon shell can be observed from short GONRs via a modified unzipping recipe. Then the short GONRs were adopted to modify the glassy carbon electrode for the electrochemical detection of ascorbic acid (AA), uric acid (UA), and dopamine (DA). Compared to other nanomaterials, cyclic voltammograms of short GONRs show higher anodic oxidation currents for AA, UA, and DA. The detection limits of three analytes are 26, 98, and 24 nM, respectively, in amperometric current-time measurements. Especially, the sensitivity for DA is improved to be 40.86 μA μM(-1) cm(-2). The improved detection signals are due to the increased active sites of the open ends of short GONRs. Moreover, the width side of short GONRs could be more active than their length side. All above-mentioned results reveal that the short GONRs can provide a novel platform for electrochemically biomarker detection of Parkinson's disease.

Fuel cells are promising alternative in automobile and stationary power generation. Direct ethanol fuel cells (DEFCs) offer significant advantages due to the non-toxicity and renewability of ethanol as well as its high power density. Development of the efficient catalysts for ethanol oxidation reaction (EOR) has attracted great attention and represents one of the major challenges in electrocatalysis. Graphene, one-atom thick nanocarbon materials, has attracted much attention recently in a variety of applications. The sulfonation of graphene is able to make it hydrophilic, which enhances its dispersibility in aqueous solvents. Furthermore, sulfonation increases the adsorption and uniform distribution of the Pt nanoparticles, which increases both the electrocatalytic activity and the durability. In this study, theoretical calculations demonstrated that the sulfonate functional group can donate charge to Pt, enhanced the adsorption energy of Pt, and then reduce the adsorption energy of CO on Pt. Then experimentally five kinds of Pt/sulfonated-graphene (Pt/sG) catalysts were synthesized via the control of pH values during the preparation of five-selected colloidal nanoparticles. Among all catalysts, Pt-sG(2.5 nm) has the highest peak current density in EOR.

We generalize a result by Stoll on the Brauer–Manin–Scharaschkin obstruction for zero-dimensional subvarieties of abelian varieties to almost split semi-abelian varieties. As consequences, we give an essentially different proof of a partial result on some exponential local–global principle over number fields, originally established by Bartolome, Bilu, and Luca, and generalize it to any global field; we also extend our consideration of this obstruction to a broader situation which has some dynamical interpretation, and improve a result by Hsia and Silverman.

Bifunctional electrocatalysts for oxygen evolution reactions (OER) and oxygen reduction reactions (ORR) are crucial to the development of regenerative fuel cells or rechargeable metal–air batteries. However, the sluggish kinetics of OER and ORR often require the use of precious metal-based catalysts such as iridium, ruthenium, and platinum to lower the energy barriers of OER and ORR. Developing a highly efficient and stable bifunctional catalyst that is made of non-precious elements for ORR and OER still remains a significant challenge. Here, we show a novel catalyst architecture based on coupling non-precious Co3O4 nanocrystals onto nitrogen-doped, core–shell structured carbon nanotube–graphene nanoribbon (N-csCNT–GNR) scaffolds prepared by microwave-assisted, controlled upzipping of multiwall carbon nanotubes. The unzipped graphene nanoribbon shell enables a high surface area for loading of Co3O4 nanocrystals while the intact inner carbon nanotube core facilitates efficient transport of electrons. The as-prepared Co3O4/N-csCNT–GNR composite catalysts exhibit remarkably high activity towards both OER and ORR as a result of synergistic interactions between Co3O4 and the N-csCNT–GNR substrates.

Monitoring biomarkers and injected theranostic nanomaterials in tissues and organs plays a pivotal role in numerous medical applications ranging from cancer diagnostics to drug delivery. Scanning electrochemical microscopy has been demonstrated as a powerful tool to create highly resolved maps of the distributions of relevant biomolecules in cells and tissues without suffering from the optical interferences of conventional microscopy. We demonstrate for the first time the application of soft microelectrodes brushing in contact mode over large and thick tissues as well as organs that were immersed in an electrolyte solution. Amperometric currents were recorded based on the local flux of redox-active species locally and specifically generated by the biomarkers and nanomaterials to create maps of the biodistribution of graphene oxide nanoribbons in mouse livers, prognostic protein biomarkers in human melanoma and redox-active proteins in mouse heart. Die Untersuchung von Biomarkern und injizierten theranostischen Nanomaterialien in Geweben und Organen spielt eine zentrale Rolle bei zahlreichen medizinischen Verfahren von der Krebsdiagnose bis hin zur Arzneimittelverabreichung. Zu diesem Zweck kann die elektrochemische Rastersondenmikroskopie hochaufgelöste Abbildungen der räumlichen Verteilung von wichtigen Biomolekülen ohne optische Interferenzen liefern. Wir haben weiche Mikroelektroden zum Abtasten großflächiger und dicker Gewebeschnitte und Organe, die in eine Elektrolytlösung eingetaucht sind, verwendet. Die Messung amperometrischer Ströme wurde durch den lokalen Fluss redoxaktiver Spezies ermöglicht, welche lokal und spezifisch durch Biomarker und Nanomaterialien in den Proben erzeugt wurden. Die biologischen Verteilungen von Graphenoxidnanostreifen in Mäuseleber, von prognostischen Proteinbiomarkern in menschlichem Hautkrebsgewebe und von redoxaktiven Proteinen in Mäuseherzen wurden separat abgebildet.

Over the function field of a smooth projective curve over an algebraically closed field, we investigate the set of S-integral elements in a forward orbit under a rational function by establishing some analogues of the classical Siegel theorem.

To use graphene oxide nanoribbons (GONRs) in combination with chemo-photothermal therapy, we modified GONRs with phospholipid-polyethylene glycol (PL-PEG) to prepare PEGylated GONRs (PL-PEG-GONRs), followed by investigation of the short-term in vivo biodistribution of 99m Tc-labeled PL-PEG-GONRs and their excretion in mice. The 99m Tc-labeled PL-PEG-GONRs demonstrated a unique biodistribution pattern of rapid accumulation in and excretion from the liver. Moreover, we determined that the PL-PEG-GNORs were excreted from the body through the renal route in urine, and we used hematological analysis to show that the PL-PEG-GNORs were not toxic in vivo . Furthermore, doxorubicin-loaded PL-PEG-GONRs had IC 50 values for chemo-photothermal therapy toward U87 glioma cells that were 6.7-fold lower than the IC 50 values in traditional chemotherapy. With these advantages, PL-PEG-GONRs could be used as drug nanocarriers to develop an efficient cancer-therapy strategy that would not only improve the efficacy of the therapy, but would also reduce the risk of side effects of the nanocarrier in the body.

In this study, the size-selected platinum (Pt) nanoparticles are loaded on sulfonated graphene with polyvinyl alcohol (PVA) as the conductive polymer for fuel-cell applications. Methanol oxidation reactions and reliability of various catalysts based on carbon black, graphene, and sulfonated graphene catalyst supports are compared under alkaline conditions. When PVA is used as the conductive polymer in place of Nafion, both the electrochemical active surface area (ECSA) and the methanol oxidation property were superior, irrespective of the catalyst and support. On the other hand, the catalyst with Pt on sulfonated graphene (Pt/sG) outperforms those on other supports. For methanol oxidation, the catalyst decay occurs with a decay of only 9.06% for Pt/sG. It is suggested that the sulfonate functional group on graphene not only improves catalytic activity but can also enhance catalyst reliability.

Graphene-supported nanoparticles (NPs) are of tremendous interests for a variety of applications recently. In this study, high-surface-area graphene powders are used for loading size-selected Pt colloidal NPs as fuel-cell catalysts for methanol oxidation reaction (MOR). It is found that the adsorption of Pt colloidal NPs on graphene surfaces is dramatically influenced by the process parameter in the mixing process. Specifically, the different solution volumes during the mixing process result in various catalyst morphologies. Pt-graphene (Pt–G) catalyst synthesized through the high-concentration solution system in the mixing process exhibits the densely-packed Pt NPs on graphene surfaces with non-flat wrinkles. Moreover, the high-density Pt NPs in the catalyst give rise to the high MOR current in its forward scan. In other words, this catalyst outperforms all the other catalysts synthesized in the low-concentration solution systems in terms of the MOR current and electrochemical surface area (ECSA). The mass activity of Pt–G-1 catalyst can reach 489.66 mA/mgPt. The appropriate loading of size-selected Pt-based NPs on graphene is significant for the controlled synthesis of catalysts for fuel-cell application.

In this study, a new core–shell heterostructure of multiwalled carbon nanotube@reduced graphene oxide nanoribbon (MWCNT@rGONR) was prepared by modified microwave-assisted synthesis step and a chemical reduction. The core–shell heterostructure of MWCNT@rGONR was used as the catalytic film of the counter electrode (CE) of a dye-sensitized solar cell (DSSC). The chemical state and the degree of defects on the surface of MWCNT@rGONR were investigated by X-ray photoelectron spectroscopy (XPS) and Raman spectra, respectively. Transmission electron microscopy (TEM) image of the film of MWCNT@rGONR shows graphene sheet, covering on a MWCNT, indicating a core of the carbon nanotube and its shell of graphene. Photocurrent density–voltage characteristics of the DSSCs, using commercial graphene nanopowder (GNP), MWCNT, and MWCNT@rGONR as the CE materials were obtained at 100 mW cm–2. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to study the electrocatalytic abilities of the films...

Graphical abstractDisplay Omitted We investigate the origin of Zr substitution in BiFeO3 films.The depth profile of XPS analysis is performed.Conduction mechanisms at gate metal/Zr-doped BFO and Zr-doped BFO/Si interfaces are investigated.The theoretical and experimental memory windows have been discussed. Metal-ferroelectric (Zr-doped BiFeO3)-insulator (HfO2)-semiconductor (MFIS) structures have been fabricated by magnetron cosputtering technique. The C-V memory windows of MFIS capacitors as functions of insulator film thickness, DC power for Zr, post-annealing temperature were compared. The leakage current that reduces with increasing the DC power results in larger memory window. The memory window increases with increasing HfO2 insulator thickness due to the effect of charge injection. In addition, the memory window increases with increasing DC power for Zr. A maximum memory window of 1.6V is obtained at the swept voltage of 8V. The temperature-dependent conduction currents of MFIS capacitors with Zr-doped BFO thin films were studied.

This review covers the electronic, optical and electrochemical properties along with electronic behaviors of boron (B) and nitrogen (N) substituted Single Wall Carbon Nanotubes (SWCNTs) underlying density functional theory (DFT) simulations. It is intended to be of interest for both experimentalists and theorists to expand application in the fields of SWCNTs. In particular, this article will focus on the electronically driven optical properties of CxNy nanotubes as a function of N concentration and BxCy nanotubes as a function of B under the action of a uniform electric field with various polarization directions through relaxed C–C bond length ab initio DFT. The link between the electronic band structure and the peak of the loss function will be highlighted. Within the formalism of DFT, we also consider the aspects of vacancy-defected SWCNTs. The effect of nitrogen incorporation is quite pronounced in enhancing the electrochemical properties of CNTs. In fact, this is a growing field due to the need of developing next-generation H-based energies. Finally, an attempt will be made for a comparative study of these theoretical results with experimental ones. Although there are ample experimental reports of N incorporation, at least less than 10%, in the nanostructured carbon, the experimental results on B-alloyed and N-alloyed SWCNTs are scarce. The review concludes with an outlook on the technological potential of these nano-composite systems as optical devices and nano-sensors.

We report here a nonenzymatic glucose sensor based on a CuO/graphene-modified screen-printed carbon electrode (CuOG-SPCE) integrated with flow-injection analysis (FIA). The highly active CuOG-SPCE with well-dispersed CuO nanoparticles on graphene surfaces performed excellent electrocatalytic oxidation of glucose. Under optimal FIA conditions, the proposed biosensor can be employed in the quantification of glucose with the linear range from 0.122 μM to 0.5 mM, the desirable sensitivity up to 2367 μA mM−1 cm−2 and the ultralow detection limit of 34.3 nM (S/N=3) simultaneously. Good repeatability of 1.92% (n=30) and less effects of common interfering species including ascorbic acid, uric acid, dopamine, fructose, lactose and sucrose were also demonstrated. The CuO-SPCE with highly sensitive, selective and stable consecutive monitoring (t=1 h) of glucose is promising for the development of an advanced nonenzymatic glucose sensor device. Keywords: Graphene, Nanoparticle, Screen-printed carbon electrode, Nonenzymatic glucose sensor, Flow-injection analysis

Glucose detection is of great importance in the fields of biological, environmental, and clinical analyses. In this study, CuO/graphene nanocomposites have been synthesized for nonenzymatic electrochemical glucose biosensors to avoid the disadvantages of enzymatic sensors. Transmission electron microscopy images show that the spherical and size-selected CuO nanoparticles were well dispersed on the surface of graphene. For the amperometric glucose detection, the low detection limit of 1 μmol L−1 with wide linear range from 1 μmol L−1 to 8 mmol L−1 can be obtained using the CuO/graphene (CuOG)-modified glassy carbon (GC) electrode with a low loading. Under the applied potential of +0.60 V vs. Ag/AgCl, the optimal CuOG-modified GC electrode exhibits a sensitivity of 1065 μA mmol−1Lcm−2. With such good analytical performance from simple process, it is believed that CuO/graphene nanocomposites are promising for the development of cost-effective nonenzymatic electrochemical glucose biosensors.

In this study, poly(3,4-ethylenedioxythiophene) (PEDOT)-modified graphene composite materials have been shown to exhibit excellent energy storage and conversion properties. Flexible, conducting and porous carbon cloth (CC) and graphene paper (GP)-modified CC (GP/CC) were used as substrates for comparison in all experiments. PEDOT was electrodeposited on these substrates, and their capacitance properties were measured for supercapacitor applications. Furthermore, the adsorption of size-selected Pt colloidal nanoparticles has also been performed using two substrates to form the electrode materials for fuel cell applications. We found that the PEDOT/GP/CC is the excellent flexible electrode material for both supercapacitors and fuel cells.

Carbon black (CB), multi-walled carbon nanotube (MWCNT), and graphene (GN) were examined as catalytic films on the counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). GN exhibits the best performance among these materials for the corresponding cell. A composite film of GN/Nafion® was next used as the catalytic film on the CE of a DSSC. Nafion® is demonstrated to be an excellent dispersant for inhibiting the aggregation of GN. A solar-to-electricity conversion efficiency (η) of 8.19% was achieved for the DSSC sensitized by TBA(Ru[(4-carboxylic acid-4′-carboxylate-2,2′-bipyridine)(4,4′-bis(5-(hexylthio)-2,2′-bithien-5′-yl)-2,2′-bipyridine)(NCS)2]), i.e., CYC-B11 dye, which was synthesized by our group, after the optimization of the composition of GN/Nafion®, and an η of 8.89% was exhibited for the cell with a sputtered-Pt (s-Pt) film on its CE under the same conditions. The significance of the cell with the composite film of GN/Nafion® lies in the fact that the expensive Pt is avoided in this case, thereby the cost of the pertinent DSSC was greatly reduced, even though its η (8.19%) is slightly smaller than that of the cell with the s-Pt film (8.89%).

Significance Four types of carbons (activated carbon, Maxsorb superactivated carbon, mesoporous templated carbon CMK-3, and graphene) were investigated as selective sorbents for adsorption of thiophene from its solution in n-octane. Graphene showed clearly the highest sulfur capacity. The relative sulfur capacities correlated well with the relative heats of adsorption. The carbene-type zigzag edge sites and the carbyne-type armchair edge sites on graphene are among the possible sites for strong interactions with thiophene.

In this study, graphene oxide nanoribbons (GONRs) were synthesized from the facile unzipping of multiwalled carbon nanotubes (MWCNTs) with the help of microwave energy. A core-shell MWCNT/GONR-modified glassy carbon (MWCNT/GONR/GC) electrode was used to electrochemically detect ascorbic acid (AA), dopamine (DA), and uric acid (UA). In cyclic voltammograms, the MWCNT/GONR/GC electrode was found to outperform the MWCNT- and graphene-modified GC electrodes in terms of peak current. For the simultaneous sensing of three analytes, well-separated voltammetric peaks were obtained using a MWCNT/GONR/GC electrode in differential pulse voltammetry measurements. The corresponding peak separations were 229.9 mV (AA to DA), 126.7 mV (DA to UA), and 356.6 mV (AA to UA). This excellent electrochemical performance can be attributed to the unique electronic structure of MWCNTs/GONRs: a high density of unoccupied electronic states above the Fermi level and enriched oxygen-based functionality at the edge of the graphene-like structures, as revealed by X-ray absorption near-edge structure spectroscopy, obtained using scanning transmission X-ray microscopy.

In this study, a graphene/Pt-modified glassy carbon (GC) electrode was created to simultaneously characterize ascorbic acid (AA), dopamine (DA), and uric acid (UA) levels via cyclic voltammetry (CV) and differential pulse voltammetry (DPV). During the preparation of the nanocomposite, size-selected Pt nanoparticles with a mean diameter of 1.7 nm were self-assembled onto the graphene surface. In the simultaneous detection of the three aforementioned analytes using CV, the electrochemical potential differences among the three detected peaks were 185 mV (AA to DA), 144 mV (DA to UA), and 329 mV (AA and UA), respectively. In comparison to the CV results of bare GC and graphene-modified GC electrodes, the large electrochemical potential difference that is achieved via the use of the graphene/Pt nanocomposites is essential to the distinguishing of these three analytes. An optimized adsorption of size-selected Pt colloidal nanoparticles onto the graphene surface results in a graphene/Pt nanocomposite that can provide a good platform for the routine analysis of AA, DA, and UA.

In this study, carbon nanotubes (CNTs) were fabricated using an arc-discharge method assisted with samarium-cobalt (Sm-Co) chloride as a catalyst. The optimal fabrication condition was determined through a series of experiments on various ambient conditions. Observations were completed using scanning electron microscopy (SEM), Raman spectroscopy, and tunneling electron microscopy (TEM); the main products we observed are well-structured multi-walled carbon nanotubes. By identifying the radial breathing modes (RBMs) of the Raman spectra with a TEM micrograph, we also observed a small number of single-walled carbon nanotubes. With the assistance of the Sm-Co chloride catalyst, the RBMs of the Raman spectra were measured in the ambient pressure of 760 torr. The TEM observations revealed that our nanotubes have good graphitic structures and almost no bamboo defects, which agrees with their Raman measurements with a high IG/ID ratio (~88). A perfect graphitic flat cap was found to be attached at the end of the nanotube. Simulation shows that by incorporating 5 carbon pentagons, it is possible to construct a flat capped carbon nanotube. The results of our experiment offer a unique approach to growing high quality CNTs. Such a flat capped structure may useful for further advanced application in nano-electronics and nano-optics.